drivers/char/softdog.c

   1 /*
   2  *      SoftDog 0.05:   A Software Watchdog Device
   3  *
   4  *      (c) Copyright 1996 Alan Cox <alan@cymru.net>, All Rights Reserved.
   5  *                              http://www.cymru.net
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License
   9  *      as published by the Free Software Foundation; either version
  10  *      2 of the License, or (at your option) any later version.
  11  *
  12  *      Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
  13  *      warranty for any of this software. This material is provided
  14  *      "AS-IS" and at no charge.
  15  *
  16  *      (c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
  17  *
  18  *      Software only watchdog driver. Unlike its big brother the WDT501P
  19  *      driver this won't always recover a failed machine.
  20  *
  21  *  03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
  22  *      Modularised.
  23  *      Added soft_margin; use upon insmod to change the timer delay.
  24  *      NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
  25  *          minors.
  26  */
  27
  28 #include <linux/module.h>
  29 #include <linux/config.h>
  30 #include <linux/types.h>
  31 #include <linux/kernel.h>
  32 #include <linux/fs.h>
  33 #include <linux/mm.h>
  34 #include <linux/miscdevice.h>
  35 #include <linux/watchdog.h>
  36 #include <linux/reboot.h>
  37 #include <linux/init.h>
  38 #include <asm/uaccess.h>
  39
  40 #define TIMER_MARGIN    60              /* (secs) Default is 1 minute */
  41
  42 static int soft_margin = TIMER_MARGIN;  /* in seconds */
  43
  44 #ifdef MODULE
  45 MODULE_PARM(soft_margin,"i");
  46 #endif
  47
  48 /*
  49  *      Our timer
  50  */
  51
  52 struct timer_list watchdog_ticktock;
  53 static int timer_alive = 0;
  54
  55
  56 /*
  57  *      If the timer expires..
  58  */
  59
  60 static void watchdog_fire(unsigned long data)
  61 {
  62 #ifdef ONLY_TESTING
  63                 printk(KERN_CRIT "SOFTDOG: Would Reboot.\n");
  64 #else
  65         printk(KERN_CRIT "SOFTDOG: Initiating system reboot.\n");
  66         machine_restart(NULL);
  67         printk("WATCHDOG: Reboot didn't ?????\n");
  68 #endif
  69 }
  70
  71 /*
  72  *      Allow only one person to hold it open
  73  */
  74
  75 static int softdog_open(struct inode *inode, struct file *file)
  76 {
  77         if(timer_alive)
  78                 return -EBUSY;
  79         MOD_INC_USE_COUNT;
  80         /*
  81          *      Activate timer
  82          */
  83         del_timer(&watchdog_ticktock);
  84         watchdog_ticktock.expires=jiffies + (soft_margin * HZ);
  85         add_timer(&watchdog_ticktock);
  86         timer_alive=1;
  87         return 0;
  88 }
  89
  90 static int softdog_release(struct inode *inode, struct file *file)
  91 {
  92         /*
  93          *      Shut off the timer.
  94          *      Lock it in if it's a module and we defined ...NOWAYOUT
  95          */
  96 #ifndef CONFIG_WATCHDOG_NOWAYOUT
  97         del_timer(&watchdog_ticktock);
  98         MOD_DEC_USE_COUNT;
  99 #endif
 100         timer_alive=0;
 101         return 0;
 102 }
 103
 104 static void softdog_ping(void)
 105 {
 106         /*
 107          *      Refresh the timer.
 108          */
 109         del_timer(&watchdog_ticktock);
 110         watchdog_ticktock.expires=jiffies + (soft_margin * HZ);
 111         add_timer(&watchdog_ticktock);
 112         return;
 113 }
 114
 115 static ssize_t softdog_write(struct file *file, const char *data, size_t len, loff_t *ppos)
 116 {
 117         /*  Can't seek (pwrite) on this device  */
 118         if (ppos != &file->f_pos)
 119                 return -ESPIPE;
 120
 121         /*
 122          *      Refresh the timer.
 123          */
 124         if(len)
 125         {
 126                 softdog_ping();
 127                 return 1;
 128         }
 129         return 0;
 130 }
 131
 132 static int softdog_ioctl(struct inode *inode, struct file *file,
 133         unsigned int cmd, unsigned long arg)
 134 {
 135         int i;
 136         static struct watchdog_info ident=
 137         {
 138                 0,
 139                 0,
 140                 "Software Watchdog"
 141         };
 142         switch(cmd)
 143         {
 144                 default:
 145                         return -ENOIOCTLCMD;
 146                 case WDIOC_GETSUPPORT:
 147                         i = verify_area(VERIFY_WRITE, (void*) arg, sizeof(struct watchdog_info));
 148                         if (i)
 149                                 return i;
 150                         else
 151                                 return copy_to_user((struct watchdog_info *)arg, &ident, sizeof(ident));
 152                 case WDIOC_GETSTATUS:
 153                 case WDIOC_GETBOOTSTATUS:
 154                         return put_user(0,(int *)arg);
 155                 case WDIOC_KEEPALIVE:
 156                         softdog_ping();
 157                         return 0;
 158         }
 159 }
 160
 161 static struct file_operations softdog_fops=
 162 {
 163         NULL,           /* Seek */
 164         NULL,           /* Read */
 165         softdog_write,  /* Write */
 166         NULL,           /* Readdir */
 167         NULL,           /* Select */
 168         softdog_ioctl,  /* Ioctl */
 169         NULL,           /* MMap */
 170         softdog_open,
 171         NULL,           /* flush */
 172         softdog_release,
 173         NULL,
 174         NULL            /* Fasync */
 175 };
 176
 177 static struct miscdevice softdog_miscdev=
 178 {
 179         WATCHDOG_MINOR,
 180         "watchdog",
 181         &softdog_fops
 182 };
 183
 184 __initfunc(void watchdog_init(void))
 185 {
 186         misc_register(&softdog_miscdev);
 187         init_timer(&watchdog_ticktock);
 188         watchdog_ticktock.function=watchdog_fire;
 189         printk("Software Watchdog Timer: 0.05, timer margin: %d sec\n", soft_margin);
 190 }
 191
 192 #ifdef MODULE
 193 int init_module(void)
 194 {
 195         watchdog_init();
 196         return 0;
 197 }
 198
 199 void cleanup_module(void)
 200 {
 201         misc_deregister(&softdog_miscdev);
 202 }
 203 #endif